What are those numbers on a Tyre

Before you begin shopping for new tyres for your car, you’d be glad to know that the information written on the sidewalls of your tyre can help you better understand your vehicle and the exact types of tyres needed for optimum performance.


Once you know where to find the information and how to decode it then you can better understand the use of these numbers. 


A tyre’s code is located on the sidewall just above the rim and beneath the brand name. It may start with a letter or series of letters. For example – P235/55 R 16 90S.

The P in front of the number indicates that the tire is designed for passenger vehicles. This is likely the first character printed on the tires of the car parked in your driveway. Another example is LT, which means the tires are made for light trucks when the letters appear at the beginning of the code.


The next part of the number sequence is the size. The three digits after the letter prefix tell you how wide the tyre is from sidewall to sidewall. A code that starts with P235, for example, has a width of 235 millimetres.


The two digits after the slash measure are called the aspect ratio. If the number is 55, it indicates that the width of the sidewall from the rim to the outer edge of the tread counts for 55% of the entire tyre width. 


The next digit that appears is an R. This is the tyre’s radial internal structure. A small fraction of tyres will have a D instead, indicating that the tyre was built using a rare crisscross pattern of internal piles.

The two digits after this letter tell you what size wheel your tyre will fit. A tyre with a 16 in this spot is designed for a 16-inch wheel.


The last digits you’ll see on your tyre are the load index and speed rating. A 90 here tells you the load the tyre is capable of bearing before it ruptures (90 equates to a maximum load of 1323 pounds). 


Look at the letter at the end of this number to determine how fast your tyres are built to go. This part of the code also requires an index chart to translate. If the letter on your tyre is S, its maximum speed is 112 mph. The chart goes up to 186 mph, which is signified with the letter Y.


Many drivers get by without ever checking these codes, but it’s helpful to know what they mean the next time you’re shopping for tyres. If you have more questions about the tyres on your car, give us a shout at TyrePro and we’ll be happy to help.